Peter Locke created a set of colored magnets called Motifo that act as giant pixels to turn your fridge into a works of art:

Each mosaic design has been specially crafted to use the same combination of pieces, so every mosaic can be made with the 1296 pieces included in each motifo pack. If you want to create a new design, just rearrange the pieces.

If I'm not afraid that they'd swallow the small pieces outright, this would be a blast for my kids! Link - via Funfurde